A couple of weeks ago, when I was in the Pacific Tuna Forum in Fiji, I posted about the presentations I was keen to hear and see. Today I present Shelton Harley's one, he is the Principal Fisheries Scientist (Stock Assessment and Modelling) of SPC's Oceanic Fisheries Programme. Shelton is a very clever man at the top of its game, and equally important, a good communicator of the science and status of the stocks.
I will attempt to pass some of his message, that was quite strong and cautionary, most of the images and graphs are self explanatory.
2014 was the largest in tuna fishery catches in history 1.96 Million Tonnes of skipjack. To make sense of this number, see above: If we were to put all the skipjack caught nose to tail, the line would extend almost half a million km... enough to go around 100000 km beyond the dark side of the moon.... that image blew my little brain off into pieces.
Every year more and more Skipjack get added to the statistics while the rest has been quite stable... but for how much more?
The Pacific catches are way more than all other oceans combined... just some Kiribati and PNG and you have more than the whole Indian ocean. This numbers are staggering.
The usual graphs that are shown, have green (is all good), orange (we need to take measures) and red (overfishing)... this time he believes that that green gives a fake sense of security... hence he circumscribed the statatus of the healtiest stocks to a smaller oval of where the fishery operates at good biological and economical returns. under that view, even skipjack looks borderline.
Hence, the overall picture is not very good for the other pelagics
Purse Seine fishing is increasing it efficiency , and there is an increase in the number of sets. Skipjack biomass is going down and catch rates are going up.
Sonar FADs (Fish Aggregation Devices) are the biggest game changer, in the past the vessel had to go to their FADs and then see if there was fish around it; with this technology fleet managers from the desk somewhere can direct the vessels to the FADs that are showing signal. Also helicopters are back in the fleet as there is lot of replacement vessels. New purse seiners are more powerful and more efficient. (And many are subsidised as i suggested before)
Of course this impact Yellowfin, as is to be seen in the 3 maps or relative abundance above. Juvenile Yellowfin associates to Skipjack and is caught with it, as purseine is not really a discriminatory fishing method.
Hence the take home message is sobering, we have long reached or exceeded long term sustainable catch levels. The harvesting at such level is also felt in nations that do not catch Skipjack, as there are ecosystems implications that are not well studied yet.
The solutions to these issues are not new:
Unfortunately, the precautionary words that he has, seems to fall in the deaf hears of most DWFN and some Pacific Islands decision makers. But good on him for bringing these issues up in public forums.
I always maintained that the region is very lucky to have organisations like SPC, that can attract and maintain scientists of Shelton's caliber. Their analytical capacity and the level of the mathematical modelling that guys like him do is quite amazing. Total respect to him.